My s21 is having same problem. Also wont charge with my power bank. At this rate atm u might aswell upgrade unless u rly want to keep the phone until it dies but its up to u.
Where are you based? If memory serves me right Samsung door step repair (where they come to you in a van) will replace with a genuine Samsung battery for £120
That's a decent price. I would recommend you check with them to confirm that it's a genuine Samsung battery they're fitting though (if this matters to you that is..)
Their terms and conditions -
We offer both high-quality after-market and OEM (genuine) parts (where possible) for the repairs of your device.